1. Field of the Invention
The present invention relates generally to a trim system of a marine propulsion device and, more particularly, to a method for causing an actuator of the trim system to move at a selected one of two actuation speeds, depending on conditions.
2. Description of the Related Art
Those skilled in the art of marine propulsion systems are aware of many different types of trim and tilt systems. Typically, trim and/or tilt systems incorporate a hydraulic cylinder connected between the transom of a marine vessel and a marine propulsion device, such as an outboard motor or a sterndrive unit.
U.S. Pat. No. 3,754,394, which issued to Morrison on Aug. 28, 1973, describes a hydraulic control system for an electric lift truck. It includes hydraulically powered mast tilting cylinders and fork hoist cylinders supplied with pressure fluid from an electric motor driven small and large capacity pair of pumps. The hydraulic circuit supplying pressure fluid to the cylinders includes a pair of spool-type metering valves, one for the tilt cylinders and one for the hoist cylinder. The hoist spool is a three-position spool having a neutral position, a lowering position and a hoisting position range. When the spool is stroked through the hoist range from low to high, fluid is metered by the spool to the hoist cylinder first at a small flow rate and gradually at increasing rates only from the small pump until the maximum flow capacity of the small pump is reached. Thereafter, as stroking continues, flow from the large pump is added gradually and progressively to the maximum flow of the small pump until the full flow capacities of both pumps is utilized to extend the hoist cylinder.
U.S. Pat. No. 3,999,502, which issued to Mayer on Dec. 28, 1976, discloses a hydraulic power trim and power tilt system supply. A hydraulic system for a combined power trim and shock absorbing piston cylinder unit of an outboard motor includes a reversible pump having a trim-up port connected by a pressure responsive pilot valve piston cylinder unit and a trim-down port through a reverse lock solenoid valve and a down-pilot spool valve providing full drain flow for trim-up and power flow for trim-down.
U.S. Pat. No. 4,050,359, which issued to Mayer on Sep. 27, 1977, discloses a hydraulic power trim and power tilt system supply. A hydraulic system for a combined power trim and shock absorbing piston cylinder unit of an outboard motor includes a reversible pump having a trim-up port connected by a pressure responsive pilot valve piston cylinder unit and a trim-down port through a reverse lock solenoid valve and a down-pilot spool valve providing full drain flow for trim-up and power flow for trim-down.
U.S. Pat. No. 4,363,629, which issued to Hall et al. on Dec. 14, 1982, describes a hydraulic system for an outboard motor with sequentially operating tilt and trim means. The device comprises a transom bracket adapted to be connected to a boat transom, a first pivot connecting a stem bracket to the transom bracket for pivotal movement of the stem bracket relative to the transom bracket about a first pivot axis which is horizontal when the transom bracket is boat mounted, a second pivot connecting a swivel bracket to the stem bracket below the first pivot for pivotal movement of the swivel bracket with the stem bracket and relative to the stem bracket about a second pivot axis parallel to the first pivot axis. A king pin pivotally connecting a propulsion unit including a rotatably mounted propeller to the swivel bracket for steering movement of the propulsion unit relative to the swivel bracket about a generally vertical axis and for common pivotal movement with the swivel bracket in a vertical plane about the first and second horizontal axes, a trim cylinder piston assembly pivotally connected to the stem bracket and to the swivel bracket, a tilt cylinder piston assembly pivotally connected to the transom bracket and to the stem bracket and a fluid conduit system communicating between a source of pressure fluid and each of the tilt cylinder piston assembly and the trim cylinder piston assembly and including apparatus operable, during reverse operation of the propulsion unit, for causing initial full extension to the trim cylinder piston assembly, followed by extension of the tilt cylinder piston assembly and for causing initial full contraction of the tilt cylinder piston assembly, followed by subsequent contraction of the trim cylinder piston assembly.
U.S. Pat. No. 4,391,592, which issued to Hundertmark on Jul. 5, 1983, discloses a hydraulic trim-tilt system. It includes a hydraulic trim-tilt piston-cylinder unit pivotally connected to both the transom bracket and the swivel bracket. Hydraulic trim piston-cylinder units are mounted in the transom bracket. A pilot operated check valve mounted in the piston of one of the trim piston-cylinder units serves to limit the maximum pressure in the system when the trim piston-cylinder units have reached the end of their stroke.
U.S. Pat. No. 4,449,365, which issued to Hancock on May 22, 1984, describes a lift, tilt and steering control for a lift truck. It includes a pair of separately controlled pumps. One pump supplies pressure fluid to a valve for a steering cylinder by way of a high priority port of a priority valve with the low priority flow passing to parallel connected lift and tilt valves which control operation of the lift cylinder and tilt cylinders, respectively. The capacity of a pump is sufficient to provide proper, effective operation of the steering and tilt functions but is not adequate to provide hydraulic fluid flow for high speed expansion of the lift cylinder. The other pump is operated to supply additional pressure fluid flow for high speed lift only when the lift valve is shifted to a raise position.
U.S. Pat. No. 4,631,035, which issued to Nakahama on Dec. 23, 1986, describes a hydraulic tilt device for a marine propulsion unit. The device employs a reversible fluid pump that drives a double acting cylinder to effect pivotal movement of the outboard drive between a tilted up and a tilted down position. The circuitry of the connection between the fluid pump and motor is such that the displaced fluid from the fluid motor need not flow through the pump during tilt down operation so that tilt down operation can be accomplished at a greater rate of speed than tilt up operation.
U.S. Pat. No. 4,929,202, which issued to Tengelitsch on May 29, 1990, describes a power trim cylinder protective locking device for an inboard/outboard boat motor. The support device maintains an outboard unit of a boat engine in a tilted position for travel. The outboard unit has a stationary driveshaft housing attached to the boat transom and a movable propeller drive unit pivotally attached with respect to the stationary drive shaft housing. A trim mechanism includes a cylinder, a hydraulically operated piston and an actuator rod engaged between the movable propeller drive unit and the stationary drive shaft housing for tilting the movable propeller drive unit to a desired angle between a lowered position and a raised position. The support device has an elongated rigid casing with a radial slot extending along the entire longitudinal length of the casing and a semi-rigid lining disposed within the casing forming a longitudinal aperture communicating with a radial slot through the casing.
U.S. Pat. No. 5,447,027, which issued to Ishikawa et al. on Sep. 5, 1995, describes a hydraulic drive system for hydraulic working machines. It includes a controller and several condition sensors. A boom-up target flow rate setting section determines a boom-up target flow rate based on signals from a pressure sensor and a rotational speed meter, a pump delivery rate detecting section determines a pump delivery rate based on signals from a tilt angle sensor and the rotational speed meter, a differential pressure detecting section and a center bypass flow rate calculating section determines a center bypass flow rate based on signals from pressure sensors, a boom cylinder calculating section determines a boom cylinder flow rate from the pump delivery rate and the center bypass flow rate, and a first pump target displacement volume calculating section calculates a first pump target tilt angle in accordance with a difference between the boom-up to target flow rate and the boom cylinder flow rate.
U.S. Pat. No. 5,969,302, which issued to Nishizawa et al. on Oct. 19, 1999, describes a lift control mechanism and method. A lift attached to a truck has a tailgate supported by at least one hydraulic lift and at least one tilt cylinder for respectively lifting the tailgate as a whole and rotating it for opening and closing. A control system for moving such a tailgate up and down as a whole and rotating it to open and close it is provided with a power unit including a hydraulic pump, an electric motor for the hydraulic pump, and a plurality of valves for selectively allowing or not allowing transport of a hydraulic liquid by the hydraulic pump into the hydraulic cylinders, a sensor for measuring the pressure inside the hydraulic pump, external switches, and a controller which includes a CPU, a timer and a semi-conductor switch and serves to calculate on real time the speed of the tailgate from signals from the sensor and the timer.
U.S. Pat. No. 6,165,032, which issued to Nakamura on Dec. 26, 2000, describes a tilt cylinder device for an outboard motor. A piston having its piston rod is extended to an outboard motor side and a free piston is freely movably inserted into a cylinder. Within the cylinder are oil chambers. An accumulator chamber is provided so as to surround the cylinder. A third communication passage is formed from the piston to the free piston.
U.S. Pat. No. 6,439,102, which issued to Matsuzaki et al. on Aug. 27, 2002, describes a tilt control device for a forklift truck. It comprises a tilt spool for operating the tilt cylinder, a pilot operation type flow rate control valve connected to the hydraulic pump via the tilt spool and adapted to be switched between a fully opened position and a half opened position which are different in opening from each other in response to addition/deletion of a pilot pressure, a pilot operation type logic valve disposed between the rod side oil compartment of the tilt cylinder and the flow rate control valve and adapted to permit hydraulic oil to flow into the rod side oil compartment and to be operated so as to open/close relative to hydraulic oil flowing out of the rod side oil compartment in response to the addition/deletion of the pilot pressure, and an electromagnetic switching valve for controlling the addition/deletion of the pilot pressure to the flow rate control valve and the logic valve.
U.S. Pat. No. 6,945,335, which issued to Suzuki et al. on Sep. 20, 2005, describes an oil pressure controlling device for an earth moving machine. An optimal pump flow for both dual tilt operations and single tilt operations is obtained at low cost without increasing the complexity of the device constitution. Where there is a wish to implement a dual tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value decreases and a comparatively small flow is supplied from the hydraulic pump to the left and right tilt cylinders. Accordingly, the extension/retraction speed of the left and right tilt cylinders decreases. Where there is a wish to implement a single tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value increases and a comparatively large flow is supplied from the hydraulic pump to the left cylinder. Accordingly, the extension/retraction speed of the left tilt cylinder increases. In this way, the tilt operating speed of the blade in dual tilt operations is made to be the same as the tilt operating speed of the blade in single tilt operations.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In typical marine operations, a marine propulsion device is subject to a trim operation in which its angle is changed relative to the transom of a marine vessel. The trim operation is performed in order to advantageously affect the operation of a marine vessel. Beyond a certain angular relationship, between the marine propulsion device and the transom, the marine propulsion device can further be tilted in order to raise it out of the water or, during transport, to raise the marine propulsion device to a position that can more easily and reliably be supported when the marine vessel is transported on a trailer. Marine propulsion devices, particularly when used in saltwater environments, are typically tilted upward to remove them from the saltwater when the marine vessel is not in use. This operation typically uses the tilt capabilities of a hydraulic system that extends beyond the range of angular positions of the marine propulsion device assumed during trimming operations.
During tilting procedures, or trimming procedures when the marine vessel is generally stationary or operating below a threshold velocity, it is desirable to move the marine propulsion device as quickly as is practical. On the other hand, when the marine propulsion device is operating under load and the associated marine vessel is moving at a speed greater than a threshold speed, it is preferred that the trimming operation be accomplished at a lesser rate of speed. It would therefore be significantly beneficial if a relatively simple and inexpensive system could be provided which allows two different rates of actuation of the hydraulic trim/tilt system.